Oh, nuts! They sure can cause you trouble if you're allergic to them — and a growing number of kids are these days.

So what kind of nuts are we talking about? Peanuts, for one, though they aren't truly a nut. (They're a legume [say: leh-gyoom] like peas and lentils.) A person could also be allergic to nuts that grow on trees, such as almonds, walnuts, pecans, cashews, hazelnuts, Brazil nuts, and pistachios.

When you think of allergies, you might picture lots of sneezing and runny noses. But unlike an allergy to spring flowers, a nut or peanut allergy can cause difficulty breathing and other very serious health problems. That's why it's very important for someone with a nut or peanut allergy to avoid eating nuts and peanuts, which can be tough because they're in lots of foods.

Why Does the Body Go Nuts Over Nuts?

When someone has a food allergy, his or her body sort of misfires. Instead of treating a nut or peanut like any old food, the body reacts as if the nut or peanut is harmful. In an attempt to protect the body, the immune system produces antibodies (special chemicals designed to fight infections) against that food.

These antibodies — called immunoglobulin E (IgE) — are designed to fight off the "invaders." IgE antibodies trigger the release of chemicals into the body. One of these is histamine (pronounced: hiss-tuh-meen). The release of histamine can affect a person's lungs, gastrointestinal tract, skin, and cardiovascular system, causing allergy symptoms like wheezing, stomachache, vomiting, itchy hives, and swelling.

Allergic Reactions

A person with nut or peanut allergies could have a mild reaction — or it could be more severe. An allergic reaction could happen right away or a few hours after the person eats a nut or peanut.

Here are some of the problems an allergic reaction can cause:

• Skin: Skin reactions are the most common type of food allergy reactions. They can take the form of itchy, red, bumpy rashes (hives), eczema, or redness and swelling around the mouth or face. A rash can happen when a nut or peanut comes in contact with the skin, even without eating it.
• Gastrointestinal system: Symptoms can take the form of belly cramps, nausea, vomiting, or diarrhea.
• Respiratory system: Symptoms can range from a runny or stuffy nose, itchy, watery eyes, and sneezing to the triggering of asthma with coughing and wheezing.
• Cardiovascular system: A person may feel lightheaded or faint.

In the most serious cases, a nut or peanut allergy can cause anaphylaxis (say: ah-nuh-fuh-lak-sis). This is a sudden, life-threatening allergic reaction in which several problems occur all at once. A person's blood pressure can drop, breathing tubes can narrow, and the tongue can swell.

People at risk for this kind of a reaction have to be very careful and need a plan for handling emergencies, when they might need to use special medicine to stop these symptoms from getting worse.

How Is a Nut or Peanut Allergy Diagnosed?

If your doctor thinks you might have a nut or peanut allergy, he or she will probably send you to see a doctor who specializes in allergies. The allergy specialist will ask you about past reactions and how long it takes between eating the nut or peanut and getting the symptom, such as hives.

The allergist also may ask about whether anyone else in your family has allergies or other allergy-related conditions, such as eczema or asthma. Researchers aren't sure why some people have food allergies and others don't, but they often run in families.

The allergist may also want to do a skin test. This is a way of seeing how your body reacts to a very small amount of the nut that is giving you trouble. The allergist will use a liquid extract of the nut that seems to be causing you trouble. (A liquid extract is a liquid version of something that usually isn't liquid.) He or she also may use liquid extracts of other common allergy-causing foods or substances.

The doctor will make a little scratch on your skin (it will be a quick pinch!). That's how just a little of the liquid nut gets into your skin. Different extracts will go on the different scratch spots, so the doctor can see how your skin reacts to each one. If you get a reddish, itchy, raised spot, it shows that you are allergic to that food or substance.

Some doctors may also take a blood sample and send it to a lab. That's where it will be mixed with some of the food or substance you may be allergic to and checked for certain antibodies.

It's important to remember that even though the doctor tests for food allergies by exposing you to a very small amount of the food, you should not try this at home! The best place for an allergy test is at the doctor's office, where they are specially trained and could give you medicine right away if you had a serious reaction.

How Is It Treated?

There is no special medicine for nut or peanut allergies and most people don't outgrow them. The best treatment is simply to avoid the nut. That obviously means not eating that nut, but it also means avoiding the nut when it's mixed in foods. (Sometimes these foods don't even taste nutty! Would you believe chili sometimes contains nuts to help make it thicker?)

Staying safe means reading labels and paying attention to what they say about how the food was produced. Some foods don't contain nuts, but are made in factories that make other items that do contain nuts. The problem there is the equipment can be used for both foods and leads to "cross-contamination." That's the same thing that happens in your own house if someone spreads peanut butter on a sandwich and dips that same knife into the jar of jelly.

After checking the ingredients list, look on the label for phrases like these:

• "may contain nuts"
• "produced on shared equipment with nuts or peanuts"
• "produced in a facility that also processes nuts"

People who are allergic to nuts also have to avoid foods with these statements on the label. Some of the highest-risk foods for people with peanut or tree nut allergy include:

• cookies and baked goods
• candy
• ice cream
• Asian and African foods
• sauces (nuts may be used to thicken dishes)

Some school cafeterias now have peanut-free tables. Talk to your doctor about whether you should be sitting at one. Also ask about how you should handle other peanut encounters, like restaurants or stadiums where lots of people are opening peanut shells. Very few people who have nut allergies will have a reaction if they are exposed only to airborne particles, but talk it over with your doctor.

Have an Emergency Plan

If you have a serious nut or peanut allergy, you and a parent should create a plan for how to handle a reaction, just in case one occurs. That way your teachers, the school nurse, your basketball coach, your friends — everyone will know what a serious reaction (anaphylaxis) looks like and how to respond.

To immediately treat anaphylaxis, doctors recommend that people with a nut or peanut allergy keep a shot of epinephrine (pronounced: eh-puh-neh-frin) with them. This kind of epinephrine injection comes in an easy-to-carry container that looks like a pen. You and your parent can work out whether you carry this or someone at school keeps it on hand for you. You'll also need to identify a person who will give you the shot.

You might want to have antihistamine medication on hand as well, though if anaphylaxis is occurring, this medicine is not a substitute for epinephrine. After receiving an epinephrine shot, you would need to go to the hospital or a medical facility, where they would keep an eye on you for at least 4 hours and make sure the reaction is under control and does not happen again.

Handling Your Nut or Peanut Allergy

If you find out you have a nut or peanut allergy, don't be shy about it. It's important to tell your friends, family, coaches, and teachers at school. The more people who know, the better off you are because they can help you stay away from the nut that causes you problems.

Telling the server in a restaurant is really important because he or she can steer you away from dishes that contain nuts. Likewise, a coach or teacher would be able to choose snacks for the group that don't contain nuts.

It's great to have people, like your parents, who can help you avoid nuts, but you'll also want to start learning how to avoid them on your own.

Reviewed by: Magee Defelice, MD, and Sheelagh M. Stewart, RN, MPH
Date reviewed: October 2011